Engine rebuild with no former experience........

Too busy to get out to the garage today, but did do some more measuring of the old and new valve guides and the head valve guide bores.

The valve guide situation is a bit odd, in EPC the original size that was used is no longer available and has been replaced by a fractionally bigger set, EPC refers to these as "repair stage 1", whereas in the workshop manual there is no mention of the original size, it refers to the EPC stage 1 as the "standard dimension". I think that at some stage when Mercedes realised that they had a problem with loose valve guides they dropped the original size and adopted the 1st oversize as the standard replacement.

Here are the old and new guides, I also purchased a single EPC oversize 2 in case I needed it for the problems I had on the intake of cylinder 1.



You can see here that the old cylinder 1 valve guide easily slips into the head.



The good news after doing all the measurement is that I wont need to bore out the head for the "oversize 2" valve guide as it is well within the recommend overlap.



Still got to check the other head but don't expect any issues there.

Next I did an inspection of all the valve seats for damage, good news again there, there were no chips or damage. They are supposed to have a 3 angle grind but its not very obvious.

Cylinder 1 exhaust



Cylinder 1 intake.



The remainder of the valve seats on the first head were the same.

Gullydeckel schrieb: Hi Jim,
Getting those parts fitted well needs some prepartion to meet the best fit alignement to the bore. The better the alignement is, the less work on the valve seat is necessary later on.

Cheers Martin

Hi Martin, I will use your more gentle method for the installation. Did you have any thoughts on the picture of the close up picture of the CAM and bearing?

I spent a long time in the garage today but made limited progress.

First I stripped down the second head.



The tray is now full!



Next was a lot of scrubbing in the hot degreaser bath.



I then checked both heads for flatness, both were good. but both heads don't look great, do you think they will seal ok or do they need skimmed?



Next I went back to the sheared bolt on the first head.



Built up with weld.



Then nut welded on.



I managed to get the bolt turning but had to go through this process a lot of times. I think the thread has galled since I am making such slow progress.



It is now sitting in a puddle of "plus gas" overnight to see if that helps.

I then went on to try to clean up the valves, I will leave them in this oven cleaner overnight, but don't have a good feeling of success. The main ingredient is Potassium Hydroxide. Does anyone have a suggestion of the best way to do this?

Hi Jim,

the camshaft bearing looks not so fine, but it may be worth a try. I wonder how this damage starts, it's the bearing closest to the oil support. The highest stress probably has the bearing on the other end, where the load of the timing chain is on. On this side I would make no compromise.

When you press in the new guides using a threaded rod, you need to lubricate the thread very well. Change the nut from time to time, as well it’s necessary to prepare a couple of thread bar pieces in advance. The stress is very high so you need to change the parts from time to time. I used copper pipes to prevent the cylinder head from damage. The copper as well won’t be very durable.

Later on try to grind as little as possible from the valve seats! The more you grind, the more new shims you need and these little things are very expensive.

Greetings Martin

Hello Jim,

smoke resin remover works very well.
One Liter in a bowl and then let time do the job.

After two days most valves were pretty clean and needed only minor add cleaning.

Kind regards

JP

Hi Martin, it is odd that the worst wear is at the back, however I have heard that this is not uncommon. The 350 engine that was fitted in my car when I bought it had very bad wear on the rear cam towers too.